I paid with a credit card, and confidently signed the sales slip with the name of Percy Cheese. Without a glance at the signature, my card was returned, my groceries were handed over, and with many bows and honorifics, I was thanked for my custom.
The Sumitomo scandal has tarnished one of the world's most powerful corporations and may yet lead to bankruptcies, resignations and criminal charges in three countries. The Camembert scandal was put right, five minutes later, with an incoherent explanation and payment in cash. But both the pseudonymous Mr Cheese and Yasuo Hamanaka, the Sumitomo copper trader who concealed his astonishing losses over 10 years, were taking advantage of the same trait in Japanese society: the remarkable extent to which personal and business relationships are based on trust.
Even Tokyo, a conurbation of 30 million people, with overcrowding and traffic which could give plenty of Third World capitals a run for their money, has at times the atmosphere of a small English village in the 1950s. It is not true that Japan is crime-free, but figures are so small as to be almost negligible. When I go out I leave windows and doors unlocked with no sense of insecurity.
The most obvious manifestation of this blissful sense of trust are hanko - personal seals, the breadth of a 5p coin, engraved with a design incorporating the owner's name in Japanese characters. Stamped on official documents, from bank withdrawals to deeds of property, they are used instead of signatures.
The advantage is that, unlike a signature, they do not require the presence of the owner. An elderly invalid can claim her pension by simply entrusting her hanko to a friend or relative. But when hanko are stolen, forged, or illicitly borrowed the consequences can be disastrous, and hanko abuse is the stuff of Tokyo urban myths.
It is not that sophisticated security measures are unavailable in Japan, but old habits of trust die hard, and are complicated by related traditions of courtesy and good service. To check signatures on credit card slips would be rude, an implication that the customer is a fraudster.
Relating such customs to fraud on the Sumitomo scale may seem naive, but not so. In September last year, Daiwa Bank announced its own massive loss in uncannily similar circumstances: a rogue trader in its New York branch lost $1.1bn over 11 years in unauthorised bond trades. Worse, it turned out that the bank and the ministry had known about the losses for months without informing the US authorities.
The director of the finance ministry's banking bureau and the head of the international finance division, two of the most powerful men in the country, gave an extraordinary press conference for the foreign media at which they attempted to justify the ministry's tardiness. The reason, we were informed, was that they could not believe such a thing could have happened in a Japanese company. Unlike the West, where fraud and its prevention are a way of life, they explained, Japanese business relationships are built on trust. Tokyo has only a fraction of the number of bank regulators of London or New York; here, a gentleman's word is his bond (even when his bonds have brought him 10-figure losses). It was this unique culture of faith and respect, rather than inadequate regulation or incompetence, which explained the failure to detect the fraud.
It seemed at the time like a brilliant and cheeky ploy not only to evade responsibility, but actually to paint Japan's ailing banking system as a Utopia, in contrast with the corrupt and iniquitous West. But yesterday, as I walked guiltily away with my cheese, I began to wonder.
Undoubtedly, Japan's corporate culture is undergoing change, and events like the Sumitomo shock will only accelerate it. Banks will supervise their employees more vigilantly, signatures will replace hanko, people will lock their apartments and credit card signatures will be scrutinised. These changes are inevitable, and will protect vulnerable people as well as rich institutions. But they will mark the extinction of something unique and touching among industrialised countries - a faith and innocence, a willingness to believe the best which, once past, will never be seen again.
Business, page 3